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[0/3] efi: arm64: Set NX compat flag where appropriate

Message ID 20230310125026.3390928-1-ardb@kernel.org
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Series efi: arm64: Set NX compat flag where appropriate | expand

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Ard Biesheuvel March 10, 2023, 12:50 p.m. UTC 
PE/COFF images that can tolerate running under a strict W^X policy when
it comes to firmware provided allocations should indicate so, by setting
the associated bit in the PE/COFF header.

Today, this makes little difference, but going forward, restricted
policies regarding secure boot and measured boot (e.g., MS Secured-core)
may refuse to run such images altogether.

Given that the zboot and arm64 EFI stub implementations do not rely on
firmware provided mappings being writable and executable at the same
time, let's set this bit.

Note that a change landed in v6.3 where we no longer tolerate this
unless we remap the relocated kernel code read-only/executable
explicitly (patch #2)

Cc: Peter Jones <pjones@redhat.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Cc: Kees Cook <keescook@chromium.org>

Ard Biesheuvel (3):
  efi/libstub: zboot: Mark zboot EFI application as NX compatible
  efi/libstub: arm64: Remap relocated image with strict permissions
  arm64: efi: Set NX compat flag in PE/COFF header

 arch/arm64/kernel/efi-header.S              | 2 +-
 drivers/firmware/efi/libstub/arm64-stub.c   | 1 +
 drivers/firmware/efi/libstub/zboot-header.S | 2 +-
 3 files changed, 3 insertions(+), 2 deletions(-)